EP0260950B1 - Recording and/or reproducing apparatus including head clogging detector means - Google Patents

Recording and/or reproducing apparatus including head clogging detector means Download PDF

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Publication number
EP0260950B1
EP0260950B1 EP87308195A EP87308195A EP0260950B1 EP 0260950 B1 EP0260950 B1 EP 0260950B1 EP 87308195 A EP87308195 A EP 87308195A EP 87308195 A EP87308195 A EP 87308195A EP 0260950 B1 EP0260950 B1 EP 0260950B1
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EP
European Patent Office
Prior art keywords
signal
head
level
pilot signals
recording
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EP87308195A
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German (de)
English (en)
French (fr)
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EP0260950A3 (en
EP0260950A2 (en
Inventor
Hiroshi C/O Patent Division Yoshioka
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Sony Corp
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Sony Corp
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Publication of EP0260950A3 publication Critical patent/EP0260950A3/en
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/455—Arrangements for functional testing of heads; Measuring arrangements for heads
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
    • G11B15/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B15/04—Preventing, inhibiting, or warning against accidental erasing or double recording
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/36—Monitoring, i.e. supervising the progress of recording or reproducing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B33/00—Constructional parts, details or accessories not provided for in the other groups of this subclass
    • G11B33/10—Indicating arrangements; Warning arrangements

Definitions

  • This invention relates to recording and/or reproducing apparatus including head clogging detector means.
  • VTR video tape recorder
  • a rotary drum 41 is provided to which a pair of magnetic heads H A and H B having azimuth angles (a slant angle of the magnetic gap relative to the scanning direction) different from each other are attached with an angular displacement of 180" therebetween.
  • a magnetic tape 42 is wrapped around the peripheral surface of the rotary drum 41 with a tape wrap angle of substantially 180°, and the tape 42 is transported in the longitudinal direction of the tape.
  • the rotary magnetic heads H A and H B are rotated through an angle of 360° while the magnetic tape 42 is transported through a distance of one frame; that is, the magnetic heads H A and H B are rotated by one revolution per frame.
  • the magnetic head H A scans the magnetic tape 42 during odd-numbered fields and the magnetic head H B scans the magnetic tape 42 during even-numbered fields.
  • the head changeover switch 44 is further supplied with a so-called RF switching pulse SWP which is synchronised with the rotating phase of the magnetic heads H A and H B to act as a changeover control signal.
  • a movable contact C of the head changeover switch 44 is connected to the terminal A in one field period during which the magnetic head H A scans the magnetic tape 42 and to the terminal B in one field period during which the magnetic head H B scans the magnetic tape 42.
  • Reproduced signals successively supplied as outputs from the changeover switch 44 are supplied to a peak detecting circuit 45, the detected output of which is supplied to a comparator 46 wherein it is compared with a reference voltage V REF .
  • the output signal from the comparator 46 indicative of the comparison result assumes a high level of "1" when the detection output from the peak detecting circuit 45 represents a normal reproduced video signal.
  • signals are picked up at a reduced level or not at all from the recorded track on the magnetic tape 42, so that the detection output assumes a low level or "0", and consequently the output signal from the comparator 46 assumes the low level of "0".
  • the output signal from the comparator 46 is supplied to a display device 47 which indicates whether or not clogging has occurred.
  • the clogged state detecting circuit described above is disclosed, for example, in Japanese Laid-Open Utility Model Publication No. 59-60724.
  • the reference voltage V REF supplied to the comparator 46 should of course be set at a level higher than the noise level. If the normal level of the reproduced video signals is assumed to be 0 dB, the noise level is approximately -20 dB. Thus, the level of the reference voltage V REF should be set at about -14 to -15 dB. However, scattering resulting from thermal characteristics and the like makes it extremely difficult to adjust the level of the reference voltage V REF with the required accuracy. If the level of the reference voltage V REF is set at too low a value, then, because of noise, the clogged state cannot be detected.
  • the clogged state detecting circuit of Figure 1 is lacking in accuracy and reliability.
  • recording and/or reproducing apparatus wherein pilot signals of different frequencies are recorded cyclically and in a predetermined sequence on parallel record tracks on a moving record medium together with an information signal organised in a series of fields and which are employed to control tracking of a reproducing head of said apparatus during reproduction of said pilot signals and said information signal, said apparatus comprising:
  • Figure 2 shows a preferred embodiment of the present invention.
  • This embodiment may be applied, for example, to a VTR in which four tracking- servo pilot signals, each having a frequency different from the frequencies of the other pilot signals, are cyclically recorded on a plurality of oblique recording tracks, and a tracking servocontrol for reproduction is effected by the use of the pilot signals.
  • the clogged state of the heads is detected upon reverse reproduction of the magnetic tape in an edit recording mode.
  • a rotary drum 1 is provided on which a pair of magnetic heads H A and H B having respective azimuth angles different from each other are located with an angular displacement therebetween of 1800.
  • a magnetic tape 2 is wrapped about the peripheral surface of the rotary drum 1 with a tape wrap angle of approximately 180°, and is transported in the longitudinal direction of the tape.
  • the magnetic heads H A and H B are rotated once per frame period.
  • the magnetic head H A scans the magnetic tape 2 in odd-numbered fields and the magnetic head H B scans the magnetic tape 2 in even-numbered fields.
  • the apparatus of Figure 2 is similar to that of Figure 1.
  • Oblique recording tracks T A and T B shown in Figure 3 are successively formed on the magnetic tape 2 by the magnetic heads H A and H B during recording. Pilot signals of four different frequencies f 1 , f 2 , f 3 and f 4 are successively recorded on the magnetic tape 2 for tracking servocontrol.
  • the frequencies of these pilot signals are cyclically changed, for example in the order f1, f 2 , f 3 , f 4 , f1, (etc.), frequency-multiplexed with a video signal (generally a composite signal formed of a low band converted chrominance signal and an FM modulated luminance signal), and then recorded.
  • the frequencies f 1 to f 4 of the pilot signals are selected to be in a lower band of the low band converted chrominance signal. For example, these frequencies may be respectively 102.544 kHz, 118.951 kHz, 165.210 kHz and 148.689 kHz.
  • the frequencies are selected such that the differences in frequency between the pilot signals satisfy the
  • a tracking control device using pilot signals substantially as described above is disclosed, for example, in our European Patent Application Publication No. EP-A-0 227 468, to which attention is directed for further details of the construction and operation of the tracking control device.
  • signals reproduced by the magnetic heads H A and H B during the reverse reproducing period in an edit recording mode are supplied through signal amplifiers 3A and 3B to respective terminals or contacts A and B of a head changeover switch 4.
  • the head changeover switch 4 is further supplied with a so-called RF switching pulse SWP which is synchronised with the rotary phase of the magnetic heads H A and H B and serves as a changeover control signal.
  • a movable contact C of the head changeover switch 4 is connected to the terminal A in each field period during which the magnetic head H A scans the magnetic tape 2 and to the terminal B in each field period during which the magnetic head H B scans the magnetic tape 2.
  • Reproduced signals successively supplied as outputs from the head changeover switch 4 are supplied to a pilot signal detecting circuit 5 formed by a low pass filter. Pilot signals detected by the pilot signal detecting circuit 5 are then supplied to a multiplying circuit 6.
  • a frequency signal generating circuit 7 locally generates signals having frequencies f 1 , f 2 , f 3 and f 4 which are supplied to a switching circuit 8.
  • the switching circuit 8 is also supplied with the RF switching pulse SWP (refer to Figure 4A) as a switching control signal.
  • the switching circuit 8 for the most part supplies signals having nominally the same frequencies as those of the pilot signals recorded on the tracks T A and T B that are respectively scanned in each field period by the magnetic heads H A and H B . However, in each period To ( Figure 4B) equal to 1/8 to 1/6 times one field period, the switching circuit 8 generates output signals REF having the same frequencies as those of the pilot signals recorded on the tracks T A and T B which are to be scanned by the magnetic heads H A and H B in the next field.
  • the frequency of the signal supplied as an output from the switching circuit 8 is successively changed from f 1 to f 2 during the period To, and changed back again to fi.
  • the frequency of the signal supplied as an output from the switching circuit 8 is successively changed from f 2 to f 3 during the period To, and changed back again to f 2 .
  • the reference pilot signal that is, the signal REF, is not limited to the period To as shown in Figure 4B, and may instead be located, for example at the beginning of each field.
  • the output signals from the switching circuit 8 are supplied to the multiplying circuit 6 as reference pilot signals.
  • each of the pilot signals from the detecting circuit 5 is multiplied with a corresponding one of the reference pilot signals from the switching circuit 8.
  • signals are obtained in the form of beat frequency outputs which are indicative of the difference in frequency between each of the reproduced pilot signals and a corresponding one of the reference pilot signals.
  • a difference or beat frequency signal at the freqency ⁇ f A ( kHz) and a difference or beat frequency signal at the frequency ⁇ f B ( 47 kHz) are supplied as outputs at the same level or amplitude.
  • the level of the beat frequency signal at the frequency ⁇ f B becomes higher than the level of the beat frequency signal at the frequency ⁇ f A .
  • the level of the beat frequency signal at the frequency ⁇ f A becomes higher than the level of the beat frequency signal at the frequency ⁇ f E .
  • the relationship of the levels of the beat frequency signals at the frequencies ⁇ f A and ⁇ f B is opposite to that in the case where the magnetic head H A scans the track T A .
  • a differential amplifier 13 is arranged to provide an indication of the head displacement from the correct tracking position.
  • a summary of the operation of the differential amplifier 13 of Figure 2 will first be given, then the operation will be described in greater detail, and then the generation of input signals S1 and S2 to the differential amplifier 13 will be described.
  • the curve shown in Figure 5a is characteristic of the output level of the differential amplifier 13, except during the period To.
  • the automatic track following (ATF) error level corresponds to the amount of head displacement, as shown by a comparison between Figures 5a and 6.
  • the beat components of 47 kHz and 16 kHz have equal levels, and the output of the differential amplifier 13 is zero.
  • the beat component of 47 kHz is maximum and that of 16 kHz is zero.
  • the beat component of 16 kHz is maximum and that of 47 kHz is zero.
  • the signal levels at the output of the differential amplifier 13 are also intermediate, as shown in Figure 5A.
  • the output of the differential amplifier 13 is thus a measure of the direction and amount of the displacement of the head from a tracking position in which it is centred on a track on which a pilot signal of specified frequency is recorded.
  • the curve shown in Figure 5B is also characteristic of the output level of the differential amplifier 13, although the timing of this curve differs from that of the curve in Figure 5A.
  • the curve in Figure 5B is produced in accordance with the tracking error amount during the period To, while the curve in Figure 5A is produced outside the period To.
  • the level of the curve in Figure 5a is used for detecting the head displacement direction and also the head displacement amount after sampling the level by a sampling pulse SHA at every field interval.
  • the curve in Figure 5B is used for detecting whether the reproducing head is located at the correct lock position as shown in Figures 5a to 5C (for example, on a track T A on which the pilot signal of frequency f 1 is recorded) or at a quasi-lock position as shown in Figures 5a to 5C (for example, on a track T A on which the pilot signal of frequency f 3 is recorded; see also Figure 3).
  • the output of the differential amplifier 13 is the same, namely zero.
  • the curve of Figure 5B can distinguish between the two cases. The operation of the differential amplifier 13 will now be described in greater detail.
  • Figures 5a illustrates the output level of the differential amplifier 13 outside the period To, when tracks on which the pilot signals with the frequencies f 1 and f 3 are recorded are reproduced.
  • the tracking displacement is zero on the abscissa, it means that the magnetic heads are in the correct tracking state, while when the tracking displacement is +4 to -4 on the abscissa, it shows respectively positive and negative displacements by one to four track widths or pitches.
  • Figure 5B illustrates the output level of the differential amplifier 13 during the period To.
  • the level of the beat frequency signal at a frequency ⁇ f A ' (where ⁇ f A ' designates the beat frequency during the period To so as to be distinguished from the beat frequency ⁇ f A outside the period To) becomes higher.
  • the level of the beat frequency signal at the frequency ⁇ f A ' becomes lower.
  • the beat component signals ⁇ f A and ⁇ f B of the reproduced pilot signals are used to detect the amount and direction of tracking displacement of the reproducing heads, while the beat component signals ⁇ f A ' and Af B ' are used to judge whether the head lock position is at a correct lock position or at a quasi-lock position which is displaced by two track widths or pitches from the correct track even though the reproducing head is apparently scanning a central portion of the tracks correctly.
  • a level "H" in Figure 5C shows a locked state.
  • the curve of Figure 5C is at a low level "L”
  • a servo operates to move the tape by two track widths or pitches to the correct lock position, as shown by solid arrows in Figure 5A. This operation is described in greater detail in the aforementioned European Patent Application Publication No. EP-A-0 227 468.
  • the output signal from the multiplying circuit 6 is supplied to a beat detecting circuit 9A formed by a band pass filter for detecting the beat frequency ⁇ f A (and also ⁇ f A ')
  • An output signal from the detecting circuit 9A is supplied to a peak detecting circuit 10A, an output signal from which is supplied to a terminal A of a changeover switch 11 and a terminal B of a changeover switch 12.
  • the output signal from the multiplying circuit 6 is also supplied to a beat detecting circuit 9B formed by a band pass filter for detecting the beat frequency ⁇ f B (and also ⁇ f B ')
  • An output signal from the detecting circuit 9B is supplied to a peak detecting circuit 10B, an output signal from which is supplied to a terminal B of the changeover switch 11 and a terminal A of the changeover switch 12.
  • the changeover switches 11 and 12 are supplied with the RF switching pulse SWP as a changeover control signal. Movable contacts C of the changeover switches 11 and 12 are respectively changed over to be connected to their respective terminals A or B at the same time as the movable contact C of the head changeover switch 4 is changed over to be connected to their respective terminals A or B.
  • Output signals S1 and S2 of the respective changeover switches 11 and 12 are supplied to the differential amplifier or comparator 13 discussed above.
  • the level of the beat frequency signal at the frequency ⁇ f A coincides with the level of the beat frequency signal at the frequency ⁇ f B if the magnetic head scans the centre portion of the tracks, as mentioned above.
  • the level of the beat frequency at the frequency ⁇ f B becomes higher than the level of the beat frequency at the frequency ⁇ f A as the magnetic head is displaced towards the preceding track.
  • the level of the beat frequency at the frequency ⁇ f A becomes higher than the level of the beat frequency at the frequency ⁇ f B as the magnetic head is displaced towards the following track.
  • the level of the output signal from the peak detecting circuit 10A becomes the same as the level of the output signal from the peak detecting circuit 10B, when the scanning position of the head is at the centre of the track. As the scanning position is displaced towards the following track, the level of the output signal from the peak detecting circuit 10A becomes higher. On the other hand, as the scanning position is displaced towards the preceding track, the level of the output signal from the peak detecting circuit 10B becomes higher.
  • the relationship between the levels of the beat frequency signals at the frequency ⁇ f A and at the frequency ⁇ f B is opposite to that in the case where the magnetic head H A scans the recording track T A . Consequently, the relationship between the levels of the output signals of the peak detecting circuits 10A and 10B is also opposite to that in the case where the magnetic head H A scans the recording track T A .
  • the movable contacts C of the changeover switches 11 and 12 are respectively changed over so as to be connected to their terminals A for one field period in which the magnetic head H A scans the recording track T A and to their terminals B for one field period in which the magnetic head H B scans the recording track T B .
  • the level of the signal S1 from the changeover switch 11 is the same as the level of the signal S2 from the changeover switch 12, if the scanning position is in the centre of the recording tracks T A and T B .
  • the level of the output signal S1 becomes higher than that of the output signal S2 as the scanning position is displaced towards the following track.
  • the level of the output signal S2 becomes higher than that of the output signal S1 as the scanning position is displaced towards the preceding track.
  • the level of the beat frequency signal at the frequency ⁇ f A ' becomes high if the scanning position is in the centre of the recording track, as described above. However, the level of the signal at the frequency ⁇ f A ' becomes lower as the scanning position is displaced towards the preceding or following track. In this case, the level of the beat frequency signal at the frequency Af B ' remains substantially zero for the period in which the magnetic head H A scans the recording track T A (only during the period To). Therefore, the level of the output signal from the peak detecting circuit 10A becomes large when the scanning position is in the centre of the recording track, and lower as the scanning position is displaced towards the preceding or following track. In this case, the level of the output signal from the peak detecting circuit 10B becomes substantially zero.
  • the level of the beat frequency signal at the frequency Af B ' becomes large if the scanning position is in the centre of the recording track, as described above.
  • the level of the beat frequency signal at the frequency Af B ' becomes lower as the scanning position is displaced towards the preceding or following track.
  • the level of the beat frequency signal at the frequency ⁇ f A ' remains substantially zero for the period in which the magnetic head H B scans the recording track T B . Therefore, the level of the output signal from the peak detecting circuit 10B becomes large when the scanning position is in the centre of the recording track, while it becomes lower as the scanning position is displaced towards the preceding or following track.
  • the level of the output signal from the peak detecting circuit 10A becomes substantially zero.
  • the movable contacts C of the changeover switches 11 and 12 are respectively changed over to be connected to their terminals A for one field period during which the magnetic head H A scans the recording track T A and to their terminals B for one period during which the magnetic head H B scans the recording track T B .
  • the level of the output signal S1 from the changeover switch 11 is large if the scanning position is in the centre of the recording tracks T A and T B .
  • the level of the output signal S1 becomes lower as the scanning position is displaced towards the preceding or following track.
  • the level of the output signal S2 from the changeover switch 12 becomes substantially zero.
  • the comparator 13 supplies an output signal at a high level if the scanning position is in the centre of the tracks, and a lower level signal as the scanning position is displaced towards the preceding or following track.
  • the output signal from the comparator 13 is supplied to a sample-and-hold circuit 14 schematically shown as comprising a connecting switch 14a and a charging capacitor 14b.
  • the sample-and-hold circuit 14 is also supplied with a control signal SHA (shown in Figure 4C) which assumes a low level "0" during the period To and a high level “1” " at other times.
  • the connecting switch 14a is turned on (closed) when the signal SHA is at the high level "1” and turned off (opened) when the signal SHA is at the low level "0".
  • the sample-and-hold circuit 14 supplies the output signal from the comparator 13 when the magnetic heads H A and H B respectively scan the recording tracks T A and T B , except during the period To; that is, the sample-and-hold circuit 14 supplies a signal of zero level when the scanning position is in the centre of the track, a positive signal of a level proportional to the degree of the displacement when the scanning position is displaced towards the following track, and a negative signal of a level proportional to the degree of the displacement when the scanning position is displaced towards the preceding track.
  • the output signal from the sample-and-hold circuit 14 is supplied, as a phase-error signal, to tape transportation apparatus 200 comprising a capstan servocircuit, a capstan motor, a driving circuit for the capstan motor, and the like.
  • tape transportation apparatus 200 comprising a capstan servocircuit, a capstan motor, a driving circuit for the capstan motor, and the like.
  • the output signal from the comparator 13 is supplied also to a sample-and-hold circuit 15 schematically shown as comprising a connecting switch 15a and a charging circuit 15b.
  • the sample-and-hold circuit 15 is also supplied with a control signal SHB (shown in Figure 4D) which assumes a high level "1" during the period To and a low level “0" at other times.
  • the connecting switch 15a is turned on (closed) when the signal SHB is at the high level "1" and turned off (opened) when the signal SHB is at the low level "0".
  • the sample-and-hold circuit 15 supplies the output signal from the comparator 13 when the magnetic heads H A and H B respectively scan the recording tracks T A and T B , only during the period To; that is, the sample-and-hold circuit 15 supplies a signal of high level when the scanning position is in the centre of the track and a signal of a lower level as the scanning position is displaced towards the preceding or following track.
  • the output signal from the sample-and-hold circuit 15 is supplied to a comparator 16 arranged to effect a hysteresis operation, for comparison with a reference voltage V REF .
  • the comparator 16 supplies a signal at a high level "1" when the output signal from the sample-and-hold circuit 15 has a higher level then the reference voltage V REF and a signal at a low level "0" when the output from the sample-and-hold circuit 15 has a lower level than the reference voltage V REF .
  • the comparator 16 supplies an output signal LOC at the high level "1" when the magnetic heads H A and H B respectively scan substantially the centre of the recording tracks T A and T B , and at the low level "0" in the other cases, as shown in Figure 4E.
  • the output signal LOC from the comparator 16 is supplied to an AND circuit 17.
  • the AND circuit 17 is also supplied with a servolock detecting pulse Po (shown in Figure 4F) timed to occur during the period To.
  • the AND circuit 17 supplies a servolock output pulse P s (shown in Figure 4G) which indicates that the magnetic heads H A and H B are scanning substantially the centre of the recording tracks T A and T B (the correct tracking state) when the comparator 16 supplies the signal LOC at the high level "1".
  • the pulse P s indicative of the servolock is supplied to a servocircuit arranged in the aforementioned tape transportation apparatus 200.
  • the servolock pulse P s supplied by the AND circuit 17 is as shown in Figure 4G, wherefrom the pulse P s ' (represented by a broken line) is removed.
  • the output signal P s from the AND circuit 17 is supplied to a system controller (not shown) comprising, for example, a microcomputer. If, for example, this servolock pulse P s is derived after a reverse reproduction of the video signal in the edit recording mode has been carried out for a predetermined time period, the VTR has its operating mode changed over from a reproducing mode to a recording mode to start recording a video signal again.
  • the pilot signals f 1 and f 4 are not recorded on the tape, so that the output signal LOC from the comparator 16 remains at the low level "0" as if the servo were released from the locked state.
  • Figure 2 also illustrates apparatus for detection of the clogged state.
  • the output of the AND circuit 17 is also connected to a clogged state detecting section 100. More specifically, the output signal from the AND circuit 17 is supplied to the inputs of AND circuits 21A and 21 B arranged in the clogged state detecting section 100.
  • the AND circuit 21 A is supplied at its other input with the RF switching pulse SWP, and the AND circuit 21 B is supplied at its other input with the RF switching pulse SWP after inversion by an inverter 22.
  • Counted output signals from the counters 23A and 23B are supplied to respective digital comparators 24A and 24B. These comparators 24A and 24B are respectively set at a reference value N REF . When the count values supplied as outputs from the counters 23A and 23B are larger than the reference value N REF , the comparators 24A and 24B respectively supply signals at the low level "0". On the other hand, when the count values supplied by the counters 23A and 23B are smaller than the reference value N REF , the comparators 24A and 24B respectively supply output signals at the high level "1". The output signals from the comparators 24A and 24B are supplied to an OR circuit 26 through respective latch circuits 25A and 25B. The output from the OR circuit 26 is then supplied to a display device 27 which is arranged to flash when the output signal from the OR circuit 26 is at the high level "1".
  • the RF switching pulse SWP is also supplied to a counter 28.
  • the counter 28 outputs a pulse P RL which rises after reverse reproduction for the edit recording mode has been carried out for a predetermined time period and falls after a predetermined time period, for example, after a ten- frame period has elapsed, as shown in Figure 4J.
  • the pulse P RL from the counter 28 is supplied to the counters 23A and 23B to reset the counters 23A and 23B at the rising edge of the pulse P RL .
  • the pulse P RL is further supplied to the latch circuits 25A and 25B so that the latch circuits 25A and 25B respond to signals supplied by the comparators 24A and 24B at the falling edge of the pulse P RL .
  • the reference value N REF set in the comparators 24A and 24B may be, for example, "8".
  • the servolock pulse P s can be derived from the AND circuit 17 in every field period in which the magnetic heads H A and H B scan the tape 2.
  • the count values of the counters 23A and 23B exceed the reference value N REF , so that the output signals of the comparators 24A and 24B assume the low level "0", and are then latched by the respective latch circuits 25A and 25B. Consequently, the output signal from the OR circuit 26 assumes the low level "0" so that the display device 26 assumes the low level "0” so that the display device 27 does not flash. In other words, the display device 27 does not indicate that clogging has occurred.
  • the pilot signal is not recorded on the recording tracks T A or T B of the tape 2 in its part to be rewound, or the pilot signal is recorded at a level which is too low to be detected.
  • the tracking servo does not operate even after reverse reproduction for the edit recording mode has been carried out for the predetermined time period. Thus, the correct tracking state cannot be ensured.
  • the servolock pulse P s cannot be derived from the AND circuit 17 in one field period in which the magnetic head H A scans the magnetic tape 2. Therefore, at the falling edge of the pulse P RL from the counter 28, the count value of the counter 23A does not exceed the reference value N REF , and the output signal from the comparator 24A assumes the high level "1", which is latched by the latch circuit 25A. Consequently, the output signal from the OR circuit 26 assumes the high level "1".
  • the servolock pulse P s cannot be derived from the AND circuit 17 during the field period in which the magnetic head H B scans the magnetic tape 2. Therefore, at the falling edge of the pulse P RL from the counter 28, the count value of the counter 23B does not exceed the reference value N REF , and the output signal from the comparator 24B assumes the high level "1", which is latched by the latch circuit 25B. Consequently, the output signal from the OR circuit 26 assumes the high level "1".
  • the output signal from the OR circuit 26 assumes the high level "1", and the display device 27 flashes or blinks to indicate that clogging has occurred.
  • the clogged state is detected on the basis of whether or not a predetermined number of the servolock pulses P s is generated in a predetermined constant time period. It is therefore possible to detect the clogged state with certainty despite the presence of noise and the like, in contrast to the situation that results when previously-proposed head clogging detection apparatus is employed. If a circuit for generating the servolock pulse P s is already provided, apparatus embodying the present invention can be manufactured inexpensively merely by adding the clogged state detecting section 100.
  • the clogged state detecting section 100 employs the counters 23A and 23B and the digital comparators 24A and 24B, the same effect can be obtained by analog operations by substituting integrating circuits, voltage comparators, and the like.
  • the clogged state detecting section 100 is embodied in hardware. However, the same operation can be effected in software fashion by the use of a microcomputer or the like.
  • the present invention may be embodied in VTR recording and reproducing apparatus or in apparatus exclusively for recording a video signal.
  • the lock state of the tracking servo is detected by the use of pilot signals, and the clogged state is detected on the basis of an output indicative of the detection result, so that the clogged state can be reliably detected despite the influence of noise and the like, in contrast to the situation that results when the previously-proposed head clogging detection apparatus is utilised.

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  • Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)
EP87308195A 1986-09-18 1987-09-16 Recording and/or reproducing apparatus including head clogging detector means Expired - Lifetime EP0260950B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP220291/86 1986-09-18
JP61220291A JPH0789405B2 (ja) 1986-09-18 1986-09-18 記録装置

Publications (3)

Publication Number Publication Date
EP0260950A2 EP0260950A2 (en) 1988-03-23
EP0260950A3 EP0260950A3 (en) 1990-03-21
EP0260950B1 true EP0260950B1 (en) 1992-12-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP87308195A Expired - Lifetime EP0260950B1 (en) 1986-09-18 1987-09-16 Recording and/or reproducing apparatus including head clogging detector means

Country Status (6)

Country Link
US (1) US4827361A (ko)
EP (1) EP0260950B1 (ko)
JP (1) JPH0789405B2 (ko)
KR (1) KR910009469B1 (ko)
DE (1) DE3783108T2 (ko)
ES (1) ES2036578T3 (ko)

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US5193033A (en) * 1988-05-17 1993-03-09 Mitsubishi Denki Kabushiki Kaisha Magnetic recording and reproducing apparatus incorporating clogging detection
JP2587475B2 (ja) * 1988-10-21 1997-03-05 株式会社日立製作所 デジタル磁気記録再生装置
KR940001539B1 (ko) * 1991-09-09 1994-02-23 삼성전자 주식회사 헤드의 이물 제거장치
SG48323A1 (en) * 1993-12-13 1998-04-17 Philips Electronics Nv Information track format and reading and recording apparatuses therefor
KR970004661B1 (ko) * 1993-12-30 1997-03-29 엘지전자 주식회사 Vcr 실시간 카운터의 진행 및 정지 제어장치
JPH08212523A (ja) * 1995-02-08 1996-08-20 Sony Corp 磁気記録再生装置
EP0905681B1 (en) 1997-09-26 2005-11-23 Matsushita Electric Industrial Co., Ltd Magnetic recording and reproducing apparatus

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JPS5940784A (ja) * 1982-08-31 1984-03-06 Sony Corp 映像再生装置
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Also Published As

Publication number Publication date
JPS6374113A (ja) 1988-04-04
KR910009469B1 (ko) 1991-11-16
EP0260950A3 (en) 1990-03-21
DE3783108T2 (de) 1993-05-27
US4827361A (en) 1989-05-02
KR880004432A (ko) 1988-06-04
EP0260950A2 (en) 1988-03-23
DE3783108D1 (de) 1993-01-28
JPH0789405B2 (ja) 1995-09-27
ES2036578T3 (es) 1993-06-01

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